C60 + nanotubes The rest of the Semester. All of Chemistry. "wrapped up" graphite. Today. Groups 1V-VIII. Metals, Insulators, Semiconductors

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1 C60 + nanotubes The rest of the Semester All of Chemistry Today "wrapped up" graphite Groups 1V-VIII Why are we excited about C60 and nanotubes Metals, Insulators, Semiconductors Conducting Soluble in different solvents Strong materials Might be useful for electronics, drug delivery, sensors... "Nanobuilding blocks" Semiconductors, bands are close but there is a gap. Need thermal energy to move into unoccupied states Or dopant (add or remove an electron)

2 Why is Silicon semiconducting while Diamond is an insulator (same structure) Graphite is sp 2 carbons A. Silicon is larger so their is less interaction between the atoms and a lower splitting between the levels B. Silicon is smaller so their is less interaction between the atoms and a lower splitting between the levels C. Silicon is larger so their is more interaction between the atoms and a greater splitting between the levels Diamond and Silicon all sp 3 Carbon (diamond) close atomic spacing leads to strong orbital overlap and large splitting between the bonding and antibonding bands INSULATOR Silicon larger atomic spacing leads to weak orbital overlap and a small splitting between the bonding and antibonding bands SEMI-CONDUCTOR

3 How might you "add an electron" to silicon? Group III will take an electron and "leave" a positive charge in the Si lattice P-doping (P = positive) A. Substitute a P for a silicon atom in the solid B. Substitute a B for a silicon atom in the solid Group V will "give an electron" and resulting in a negative charge in the Si lattice N-doping (N = negative) C. Substitue a C for a silicon atom in the solid Last but not least Silicone (rubber) Back bone...-si-o-si-o-si-o-si-o-... Silicon can form two more bonds Add various organic molecules for different properties household "caulk", silly putty,...

4 Group V, VI, VII 4 Largest Production Chemical in the US Four very important chemicals Phophoric Acid (H3PO4) Ammonia (NH3) Sulfuric Acid (H2SO4) Chlorine Gas (Cl2) Sulfuric Acid used for lots of things Steel production Phosphoric Acid Production Recovery of Ammonia in Steel Production Industrialized Nation = Nation with lots of Sulfuric Acid Oxidizing Agent Strong Acid Dehydrating Agent

5 Fertilizer Ammonia (N source) + Phosphoric Acid (P source) Ammonia used to make Nitric Acid (Ostwald Process) 2NH3(g) + 4O2(g) 2HNO3(aq) + 2H2O(l) HNO3(aq) + NH3(g) NH4NO3(s) Sulfuric Acid used to make soluble phosphates Ca3(PO4)2 + 2H2SO4 2CaSO4 + Ca(H2PO4)2 Uses Production 3H2(g) + N2(g) Ammonia Haber Process catalyst 2NH3(g) Weak base (cleaning agent) Refrigerant (no longer used) fertilizer nitric acid production the Many NO compounds N2O nitrous oxide (anaesthesia) NO neurotransmitter NO2 brown gas (NOx smog) also NO2 + OH = HNO3 = acid rain

6 Group VI Important Chemistry Nearly everything oxidizes Lots of oxides very stable Sulfur Chemistry H2SO4 very important see previous comments Halogens Need one electron to make a nobel gas structure Excellent oxidizing agents High ionization energies Small atoms and ions Large electronegativities

7 Lot's of Chemistry Cl2 Used for halogenating compounds also used as a disinfectant Very poisonous (highly reactive) "pool chlorine" HOCl Cl2 + H2O HOCl + HCl "chlorine bleach" NaOCl OCl - is a strong oxidizing agent Fluorine unusual High charge density makes more insoluble salts Nobel Gases Few reactions. Nearly all with Xe (highly polarizable) Also fluorinated compounds tend to be very stable and can have unique properties polytetrafluoroethylene (Teflon)